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Title: Ag Nanoparticles Supported on Yttria-Stabilized Zirconia: A Synergistic System within Redox Environments

In this paper, we report a distinctive dynamic sintering-free redox behavior of Ag nanoparticles (AgNPs) on 30 nm thick yttria-stabilized zirconia (YSZ) films. The material system demonstrates reversible 200 nm shifts in the plasmonic spectra with an unprecedented particle phase/size/morphology oscillation during cyclic redox reactions in air and hydrogen/air at 300–400 °C. This is in significant contrast to the minor changes more commonly observed for AgNPs on quartz. It was found that the ionically active YSZ has a strong tendency to drive AgNPs to oxidize under oxidizing conditions, and upon surface oxidation a large differential surface energy is built up, forcing the core/shell particles to migrate and coalesce toward a lower system free energy. Most strikingly, once switched to a mixture of H 2 and air, the previously formed large dewetted metal-core/thick oxide-shell particles collapse, and new small Ag nanoparticles quickly form and remain in a highly dispersed and sintering-free state on YSZ. This is found to likely be due to catalytic production of water over the material system, which plays a key role in the dynamic redox activities. It is hypothesized that the small metallic particle regeneration and sinter-free behavior take place through a four-step process resulting from themore » synergistic behavior of AgNPs supported on YSZ within a redox environment: (I) production of a local humid environment via catalytic reactions of H 2 and O 2 mostly at the triple-phase boundary, (II) dissolution of Ag + from both reduced Ag and the AgO x shell, (III) collapse and spillover of the AgO x shell/water layer with Ag ions onto the hydrous YSZ surface, and (IV) reduction, diffusion, nucleation, and growth to new small metallic AgNPs with a dynamic equilibrium quickly reached. As a result, the findings behind this novel system could set up an avenue for a new concept of catalysts operating in a self-controlled dynamic regime for governing chemical reactions via metal and ceramic synergized catalysis with high activities and stabilities.« less
Authors:
 [1] ;  [1] ;  [2] ;  [2] ;  [1]
  1. SUNY Polytechnic Institute, Albany, NY (United States)
  2. National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States)
Publication Date:
Grant/Contract Number:
PN1006399; FE0007190
Type:
Accepted Manuscript
Journal Name:
Journal of Physical Chemistry. C
Additional Journal Information:
Journal Volume: 120; Journal Issue: 9; Journal ID: ISSN 1932-7447
Publisher:
American Chemical Society
Research Org:
National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
08 HYDROGEN; Ag Nanoparticles; catalysis; YSZ films; plasmonically active
OSTI Identifier:
1477742

Zhao, Zhouying, Rossi, V. A. Vulcano, Baltrus, John P., Ohodnicki, Paul R., and Carpenter, Michael A.. Ag Nanoparticles Supported on Yttria-Stabilized Zirconia: A Synergistic System within Redox Environments. United States: N. p., Web. doi:10.1021/acs.jpcc.6b00189.
Zhao, Zhouying, Rossi, V. A. Vulcano, Baltrus, John P., Ohodnicki, Paul R., & Carpenter, Michael A.. Ag Nanoparticles Supported on Yttria-Stabilized Zirconia: A Synergistic System within Redox Environments. United States. doi:10.1021/acs.jpcc.6b00189.
Zhao, Zhouying, Rossi, V. A. Vulcano, Baltrus, John P., Ohodnicki, Paul R., and Carpenter, Michael A.. 2016. "Ag Nanoparticles Supported on Yttria-Stabilized Zirconia: A Synergistic System within Redox Environments". United States. doi:10.1021/acs.jpcc.6b00189. https://www.osti.gov/servlets/purl/1477742.
@article{osti_1477742,
title = {Ag Nanoparticles Supported on Yttria-Stabilized Zirconia: A Synergistic System within Redox Environments},
author = {Zhao, Zhouying and Rossi, V. A. Vulcano and Baltrus, John P. and Ohodnicki, Paul R. and Carpenter, Michael A.},
abstractNote = {In this paper, we report a distinctive dynamic sintering-free redox behavior of Ag nanoparticles (AgNPs) on 30 nm thick yttria-stabilized zirconia (YSZ) films. The material system demonstrates reversible 200 nm shifts in the plasmonic spectra with an unprecedented particle phase/size/morphology oscillation during cyclic redox reactions in air and hydrogen/air at 300–400 °C. This is in significant contrast to the minor changes more commonly observed for AgNPs on quartz. It was found that the ionically active YSZ has a strong tendency to drive AgNPs to oxidize under oxidizing conditions, and upon surface oxidation a large differential surface energy is built up, forcing the core/shell particles to migrate and coalesce toward a lower system free energy. Most strikingly, once switched to a mixture of H2 and air, the previously formed large dewetted metal-core/thick oxide-shell particles collapse, and new small Ag nanoparticles quickly form and remain in a highly dispersed and sintering-free state on YSZ. This is found to likely be due to catalytic production of water over the material system, which plays a key role in the dynamic redox activities. It is hypothesized that the small metallic particle regeneration and sinter-free behavior take place through a four-step process resulting from the synergistic behavior of AgNPs supported on YSZ within a redox environment: (I) production of a local humid environment via catalytic reactions of H2 and O2 mostly at the triple-phase boundary, (II) dissolution of Ag+ from both reduced Ag and the AgOx shell, (III) collapse and spillover of the AgOx shell/water layer with Ag ions onto the hydrous YSZ surface, and (IV) reduction, diffusion, nucleation, and growth to new small metallic AgNPs with a dynamic equilibrium quickly reached. As a result, the findings behind this novel system could set up an avenue for a new concept of catalysts operating in a self-controlled dynamic regime for governing chemical reactions via metal and ceramic synergized catalysis with high activities and stabilities.},
doi = {10.1021/acs.jpcc.6b00189},
journal = {Journal of Physical Chemistry. C},
number = 9,
volume = 120,
place = {United States},
year = {2016},
month = {2}
}